Nissan ECU Diagnosis Without CONSULT Tool

In this article we will be using a Z32 for basic ECU diagnosis to retrieve DTCs for pre-OBDII vehicles. Nissan offers CONSULT tests for a fee to pinpoint problems through the ECU. There are procedures to get some of the same results without a CONSULT tool from the ECU’s memory.

Skill Level 2 of 5

Time Required < 1hr.

Procedure

1. Remove the passenger floor mat.

2. Pull back carpet. It’s held up with 3 spots of velcro.

3. Remove the wooden floorboard (4 x 10 mm bolts)

4. The screw potentiometer is on the right side of the ECU, the coding LED is in the oval hole above it.

9. Start engine with the ECU in MODE II to enter MODE II – Heated Oxygen Sensor (O2) Monitor . The ECU is now monitoring the left O2 sensor. Warm the engine to normal operating temperature, then run at 2000 rpm for 2 minutes. Check that the LED blinks (or the check engine light) more than 5 times every 10 seconds at 2000 rpm.

10. To change to right sensor turn the ECU potentiometer clockwise with engine still running, wait 2 seconds, turn it back. Check the lights at 2000 rpm again for a similar switching condition.

Note: Light indicates signal from sensor to ecu. ON=rich, Off=lean. Blinking light means system is constantly adjusting between lean and rich which is normal. Any other indication would be abnormal and require further investigation. The switched on/off is ‘closed loop’, while a constant on or off is ‘open loop’

This section includes the following: Trouble Code Detected Items Malfunction Caused By Check

11* Camshaft Angle Sensor circuit (CAS) Either 1° or 120° signal is not entered for the first few seconds of engine cranking. Either 1° or 120° signal is not input often enough while the engine speed is higher then the specified RPM. Check harness and connector (if harness and connector are OK, CAS might be bad)

12 Mass Air-Flow Sensor circuit (MAS) The MAS sensor circuit is open or shorted (abnormally high or low voltage is registered). Check harness and connector (if harness and connector are OK, MAS might be bad)